Various different types of gas compressors to compress a wide range of gases are known. Hydraulic gas compressors in particular are used in a number of different applications. One such category of, and application for, gas compressors is a gas compressor employed in connection with the operation of oil and gas producing well systems. When oil is extracted from a reservoir using a well and pumping system, it is common for natural gas, often in solution, to also be present within the reservoir. As oil flows out of the reservoir and into the well, a wellhead gas may be formed as it travels into the well and may collect within the well and/or travel within the casing of the well. The wellhead gas may be primarily natural gas and also includes impurities such as water, hydrogen sulphide, crude oil, and natural gas liquids (often referred to as condensate).
The presence of natural gas within the well can have negative impacts on the functioning of an oil and gas producing well system. It can for example create a back pressure on the reservoir at the bottom of the well shaft that inhibits or restricts the flow of oil to the well pump from the reservoir. Accordingly, it is often desirable to remove the natural gas from the well shaft to reduce the pressure at the bottom of the well shaft, particularly in the vicinity of the well pump. Natural gas that migrates into the casing of the well shaft may be drawn upwards—such as by venting to atmosphere or connecting the casing annulus to a pipe that allows for gas to flow out of the casing annulus. To further improve the flow of gas out of the casing annulus and reduce the pressure of the gas at the bottom of the well shaft, the natural gas flowing from the casing annulus may be compressed by a gas compressor and then may be utilized at the site of the well and/or transported for use elsewhere. The use of a gas compressor will further tend to create a lower pressure at the top of the well shaft compared to the bottom of the well shaft, assisting in the flow of natural gas upwards within the well bore and casing.
There are concerns in using hydraulic gas compressors in oil and gas field environments, relating to the potential contamination of the hydraulic fluid in the hydraulic cylinder of a gas compressor from components of the natural gas that is being compressed.
There are additional concerns in inefficient hydraulic gas compressor operation and increased costs associated with using such compressors.
Improved gas compressors and control systems and methods are desirable, including gas compressors employed in connection with oil and gas field operations including in connection with oil and gas producing wells.